The 25-year-old singer upsets the odds and sees his self-produced second album pick up the prestigious music award.
James Blake has been named this year's Mercury Prize winner for his Overgrown album, beating bookies' favourite Laura Mvula.
The 25/1 outsider from London collects a £20,000 prize and the coveted winner's trophy.The winner also normally sees a healthy sales boost in the days and weeks after the announcement.
Blake, 25, was nominated for the Mercury in 2011 for his self-titled debut album, and has previously been up for two Brit awards.
The Goldsmiths graduate's latest work was described by judges as "late night music for the digital age".
Blake bags a £20,000 winner's cheque
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The Arctic Monkeys, winners in 2006, made it on to the list for a third time
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Rudimental made the shortlist for the first time this year
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Electronic duo Howard (L) and Guy Lawrence (R) of Disclosure arrive at The Roundhouse in Camden
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Conor O'Brien of Irish indie folk band Villagers, who make their second appearance on the nominations list
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Savages got their first nomination and a chance at the £20,000 prize
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Foals frontman Yannis Philippakis, second left, is said to have fought off the flu to open the show
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Nottingham singer-songwriter Jake Bugg, 19, makes his debut at this year's Mercury Prize
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Laura Mvula's debut album Sing to the Moon made the nomination shortlist
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The self-produced album also features contributions from Brian Eno and RZA from Wu-Tang Clan.
Speaking at the awards, Blake thanked his parents for teaching him to be "self-sufficient".
Asked what he would spend the money on, he said: "I can tell you what I'm not going to do with it, **** it up the wall.
"I'll make sure it goes to some good use."
The 12 nominees for the Mercury included the likes of David Bowie, Arctic Monkeys and Jake Bugg.
Bowie, who now rarely plays live, was the only one of the shortlisted acts to not perform at the event at north London's Roundhouse.
Bookmakers had made Birmingham-born soul singer Laura Mvula 4/6 to win followed by electronic duo Disclosure, rockers Foals and David Bowie.
Earlier in the night, host Lauren Laverne mistakenly introduced Blake as "James Blunt".
She apologised on Twitter for the slip up, posting: "Never felt better than I do tonight about artists who have fractionally dissimilar fore and surnames. #MercuryPrize #Irony."
Alt-J won last year's Mercury award for their album An Awesome Wave.
The £20,000 prize is open to British and Irish acts and is known for giving exposure to up and coming musicians.
However, some people criticised this year's shortlist as featuring too many mainstream artists.
